Just began my "trial" of Redshift which is more or less an open-source Linux version of f.lux. The tool uses your location and adjusts the color temperature of your screen at night. That should, in principle, make the computer screen easier on the eyes, especially when the ambient lighting in the room is not well.
Because the bundled geoclue service did not work for me (and Redshift failed to start), I manually added my location to the config file. Just put the following into
[redshift] location-provider=manual [manual] lat=35.95 lon=47.13
In this example, I entered the average latitude and longitude of Kurdistan. You need to replace them with the values for your place. Try latlong.net.
After this change, I was able to start
redshift-gtk. The tool sits in the system tray and automatically applies the suitable color temperature for the current day time. From the tray, you can also configure it to automatically start on every login. See the homepage for details.
Really cool for long hacking nights! ;-P